The present invention relates to a valve arrangement, and in particular to a check valve arrangement for a test point for taking pressure measurements or fluid samples in pressurised fluid systems, including gaseous systems.
Test points are used to provide testing or measuring connections for pressurised fluid lines of hydraulic or gas systems. Typically a test point is incorporated into a fluid line of a hydraulic or gas system to provide a means by which a pressure measuring device can be connected to the system in order to measure fluid pressure within the system. The test points are also used for obtaining samples of the fluid (gas or liquid) from the system without the requirement of disrupting the system to obtain the sample, and without spillage or other problems which may be encountered. The test point includes a valve arrangement, commonly known as a check valve, to provide for opening and closing of the test point.
Known check valves have included the use of a xe2x80x9cball valvexe2x80x9d arrangement whereby a ball and seat arrangement provides a one-way valve which can be used to obtain pressure measurements and samples. Problems arose with the usage of such ball valves as leakage or weeping is difficult to control in such systems, particularly when gaseous fluids are being used. Poppet type valves have also been used, and these overcome some problems associated with the ball and seat arrangements.
One problem associated with known poppet type check valves of test points is that it is typical for the seal carried on the movable valve body to be pinched between the valve body and the bore of the valve housing during closing of the check valve under pressure. In particular, the seal may be distorted from its desired shape under the action of the fluid pressure and is often forced into the gap between the valve body and the valve housing during the closing of the check valve, thereby pinching the seal. This effect during closing of the check valve leads to damage of the seal and subsequent premature failure.
A further problem with known test points for pressurised fluid systems is that there is a limitation upon the fluid pressure at which the test point can be opened by hand in order to take a pressure reading. Typically, known test points have an upper limit of approximately 6000 psi (≈42 MPa) xe2x80x9cbreak inxe2x80x9d pressure; that is, it is difficult if not impossible to open the test point by hand at pressures in excess of approximately 6000 psi (≈42 MPa). This is because a worldwide standard has been developed in this field of technology, and this standard utilises a connection thread of 16mm by 2mm pitch. Any change to this thread would cause significant problems as existing tools and probe attachment apparatus would no longer fit to the new test points. As such it is generally not feasible to overcome this problem by reducing the pitch of the thread. At pressures in excess of 6000 psi (≈42 MPa) it is usually necessary to use a tool on the 16mm by 2mm pitch attachment nut in order to provide sufficient torque to the nut to subsequently provide sufficient force to the attachment probe to open the test point. Such a limitation is particularly undesirable.
It is an object of the present invention to provide a check valve arrangement for a test point for taking pressure measurements or fluid samples in a pressurised fluid system which overcomes at least one shortcoming in prior art designs of check valves.
It is also an object of the present invention to provide a test point for taking pressure measurements or fluid samples in a pressurised fluid system which overcomes at least one shortcoming in prior art designs of test points.
One aspect of the present invention includes a check valve for a test point, said check valve configured to receive a measurement probe having a probe diameter, said check valve including:
a housing defining a stepped bore, said stepped bore defining an upper bore portion having all upper diameter and a lower bore portion having, a lower diameter, said lower diameter being less than either said upper diameter or the probe diameter, and
a movable valve body located in said lower bore portion, said movable valve body having, a body diameter less than said upper diameter or the probe diameter.
The present invention also provides a test point for taking pressure measurements or fluid samples in a pressurised fluid system, said test point including a check valve including:
a housing having a bore and a movable valve body located in said bore, one end of said housing adapted to receive a pressure measuring probe for taking said pressure measurements or fluid samples, said one end of said housing including a upper bore portion within which, in use, said pressure measuring probe is located,
wherein said movable valve body includes an end located in said upper bore portion of nominal diameter less than the nominal diameter of said upper bore portion.
Advantageously this aspect of the present invention enables a smaller diameter valve body to be used in conjunction with a conventional pressure testing probe. This in turn leads to a reduction in the force required to open the check valve in order to take a pressure reading and thereby enables the check valve to be opened at higher pressures without the need for tools.
A further aspect of the present invention provides a check valve for a test point for taking pressure measurements or fluid samples in a pressurized fluid system, said check valve including:
a housing with a bore passing therethrough;
a movable body located in said bore for providing opening and closing of said check valve; and
a seal located oil said movable valve body for providing a sealing between check valve body and said bore,
wherein said check valve includes a collar means engaged on said movable valve body and movable thereon to support said seal and said collar provides a supporting surface for the seal and acts to ensure the seal maintains its desired shape under the effect of fluid pressure during, opening and closing of the check valve.
The present invention also provides a test point for taking pressure measurements or fluid samples in a pressurised fluid system, said test point including a check valve including:
a housing with a bore passing therethrough,
a movable valve body located in said bore for providing opening and closing of said check valve,
a seal located on said movable valve body for providing sealing between said valve body and said bore,
wherein said check valve includes a collar means located on said movable valve body to support said seal.
Advantageously the collar provides a supporting surface for the seal and acts to ensure the seal maintains its desired shape under the effect of fluid pressure during the opening and closing of the check valve. Preferably the collar is engaged on the valve body and movable thereon.